This phrase has been around for a couple of centuries now and comes from the London criminal underworld.
Well known for its use of cockney rhyming slang, phrases aren’t always what they appear to be.
The traditional shout of “stop thief!” was mocked by being replaced by “hot beef, hot beef” in criminal circles where it was thought that the shouts of “stop thief” were nothing more than making fuss about nothing.
The 1811 edition of the “Dictionary of the Vulgar Tongue” defines Beef as: “to cry beef; to give the alarm.”